This invention relates to a restrictor device for use in restricting the extent of opening of an openable closure and more particularly a window.
Restrictor devices for limiting the extent of opening of a window sash for security and safety purposes are known. Such restrictor devices can, for example, limit the opening of the sash so as to provide for ventilation but prevent unauthorised entry from the outside through the window. Such restrictor devices are also useable to provide safety so as to prevent a window sash opening to such an extent that, say, a small child could pass through the gap between the open sash and the window frame. Additionally a restrictor device can limit the extent of opening so as to prevent, in the event of uncontrolled opening, a person from being drawn through the window opening.
On exceptionally large window sashes restrictor devices can also provide additional control of the sash when friction stays are fitted. Furthermore, when the sash is simply hung on hinges the restrictor device provides the sole means of control of the extent of opening and in many cases maintenance of the sash in the open position.
Restrictor devices whether they be for security or safety purposes or simply to control the sash suffer from a number of drawbacks. For example, they are not versatile in operation in that they usually provide control only at specific degrees of openness of the sash. Furthermore they usually only provide control in one direction. Even further, some restrictor devices can become disengaged upon a force in the opening direction arising, eg due to a wind gust. Such disengagement will permit the sash to slam closed resulting in damage and/or physical danger to someone attending the window or can result in the security/safety purpose of the restrictor being lost.